Precise estimation of arrival time of switching events close in time and space

Abstract

Methods and systems for estimating arrival time of switching events include measuring two or more emission events from a device under test under different skew conditions. The two or more emission events are close in time and space when no skew condition is applied. The measured waveforms of the two or more emission events are analyzed with associated skew conditions to determine a skew value that corresponds with a time separation between the two or more emission events.

What is claimed is: 
     
       1. A method for estimating arrival time of switching events, comprising:
 testing a device under test under a plurality of different skew conditions by applying test patterns to the device under test; 
 measuring two or more emission events from the device under test under each of the plurality of different skew conditions using an imaging tool, wherein the two or more emission events are close in time and space when no skew condition is applied; and 
 analyzing measured waveforms of the two or more emission events with associated skew conditions, using a processor, to determine a skew value that corresponds with a time separation between the two or more emission events. 
 
     
     
       2. The method of  claim 1 , wherein analyzing the measured waveforms comprises:
 averaging measured waveforms; 
 subtracting the averaged waveform from an non-skewed waveform to generate a remainder waveform; and 
 calculating a difference between the averaged waveform and the remainder waveform. 
 
     
     
       3. The method of  claim 2 , wherein a time of at which the non-skewed waveform is acquired is proportional to an aggregate acquisition time for the averaged waveforms. 
     
     
       4. The method of  claim 1 , wherein analyzing the measured waveforms comprises:
 plotting emission event peak timing as a function of skew value; and 
 determining a skew value that maximizes the emission event peaks. 
 
     
     
       5. The method of  claim 4 , wherein determining the skew value that maximizes emission event peaks comprises interpolating between measured skew values according to a fitting model. 
     
     
       6. The method of  claim 1 , wherein analyzing the measured waveforms comprises:
 calculating a full width at half maximum (FWHM) for emission peaks in each measured waveform; 
 locating regions in a plot of FWHM values against skew value that have elevated FWHM values; and 
 determining a skew value that corresponds to a minimal FWHM value between the located regions. 
 
     
     
       7. The method of  claim 1 , wherein analyzing the measured waveforms comprises:
 generating fitting models for each emission event across the plurality of different skew conditions in regions where the emission events can be separated; and 
 determining a skew value that corresponds to an intersection between two fitting models. 
 
     
     
       8. The method of  claim 1 , wherein analyzing the measured waveforms comprises:
 generating a fitting model for a time separation between two emission events across the plurality of skew conditions in regions where the emission events can be separated; and 
 determining skew value that corresponds to an a value of zero for the fitting model. 
 
     
     
       9. The method of  claim 1 , wherein the skew conditions comprise one or more tunable variables on the device under test. 
     
     
       10. The method of  claim 1 , wherein the skew conditions comprise one or more noise sources. 
     
     
       11. A computer readable storage medium comprising a computer readable program, wherein the computer readable program when executed on a computer causes the computer to perform the steps of  claim 1 . 
     
     
       12. A system for estimating arrival time of switching events, comprising:
 a pattern generator configured to apply test patterns to test a device under test under a plurality of different skew conditions; 
 an imaging tool configured to measure two or more emission events from a device under test under each of the plurality of different skew conditions, wherein the two or more emission events are close in time and space when no skew condition is applied; and 
 a waveform analysis module comprising a processor configured to analyze measured waveforms of the two or more emission events with associated skew conditions to determine a skew value that corresponds with a time separation between the two or more emission events. 
 
     
     
       13. The system of  claim 12 , wherein the waveform analysis module is further configured to average measured waveforms, to subtract the averaged waveform from an non-skewed waveform to generate a remainder waveform, and to calculate a difference between the averaged waveform and the remainder waveform. 
     
     
       14. The system of  claim 13 , wherein a time at which the non-skewed waveform is acquired is proportional to an aggregate acquisition time for the averaged waveforms. 
     
     
       15. The system of  claim 12 , wherein the waveform analysis module is further configured to plot emission event peak timing as a function of skew value and to determine a skew value that maximizes the emission event peaks. 
     
     
       16. The system of  claim 15 , wherein the waveform analysis module is further configured to interpolate between measured skew values according to a fitting model to determine the skew value that maximizes emission event peaks. 
     
     
       17. The system of  claim 12 , wherein the waveform analysis module is further configured to calculate a full width at half maximum (FWHM) for emission peaks in each measured waveform, to locate regions in a plot of FWHM values against skew value that have elevated FWHM values, and to determine a skew value that corresponds to a minimal FWHM value between the located regions. 
     
     
       18. The system of  claim 12 , wherein the waveform analysis module is further configured generate fitting models for each emission event across the plurality of different skew conditions in regions where the emission events can be separated and to determining a skew value that corresponds to an intersection between two fitting models. 
     
     
       19. The system of  claim 12 , wherein the waveform analysis module is further configured to generate a fitting model for a time separation between two emission events across the plurality of skew conditions in regions where the emission events can be separated and to determine skew value that corresponds to an a value of zero for the fitting model. 
     
     
       20. The system of  claim 12 , wherein the skew conditions comprise one or more noise sources.